1. Field of the Invention
The invention relates to a process for preparing difluoromethoxy derivatives of aromatic aldehydes and is useful in the chemical technology.
Difluoromethoxy derivatives of aromatic aldehydes are used in organic synthesis to obtain compounds possessing physiological activity. The scope of intended use of said compounds has not been yet exhausted. Difluoromethoxy derivatives of aromatic aldehydes may also be used for preparing dyes, pesticides etc. However, the complexity of the process of synthesizing said compounds does not allow these compounds to be used on a commercial scale. Therefore there is a problem of developing more straightforward processes for preparing difluoromethoxy derivatives of aromatic aldehydes.
2. Description of the Prior Art
Known in the art is a process for preparing derivatives of benzaldehyde containing difluoromethoxy-, difluoromethyl thio- or difluoromethylsulfonyl groups (USSR Inventor's Certificate No. 595281). Said compounds are prepared by treating an anilide of a corresponding substituted benzoic acid with phosphorus pentachloride, followed by reducing the resulting imido chloride with stannum dichloride in the medium of an anhydrous diethyl ether saturated with hydrogen chloride, and further hydrolyzing the reaction mixture with an aqueous solution of hydrochloric acid.
The yield of the end product is 77% calculated as the starting anilide. If the calculation is carried out on a hydroxybenzoic acid, the yield is 26 to 46%.
However, the process above described is complex and laborious. Besides, in the process of synthesis, a large amount of raw materials, such as aniline, phosphorus pentachloride, stannum dichloride saturated with hydrogen chloride, diethyl ether, hydrochloric acid, is used, thus involving considerable expenses to practice the process.